The invention relates to a storage technique, and more specifically to a method and apparatus for data migration between storage devices.
A mass storage system often consists of various types of storage devices, and these storage devices range widely in price and performance. For example, reading a copy of data from a hard disk driver (HDD) with 15000 revolutions per minute (RPM) needs an average response time of 10 ms, whereas reading the data directly from a solid state disk (SSD) needs an average response time of less than 1 ms. However, the cost of a high speed storage device is higher than that of a low speed storage device, and a data capacity of the high speed storage device in the system is less than that of the low speed storage device. Therefore, only a part of data will be stored in the high speed storage device.
It is provided that: in the storage system, the smallest unit of data is a data block; a plurality of data blocks form a data volume; and an application requests one or more data volumes. It can be determined, from a frequency of data access, which data need to be stored in the high speed storage device, thereby migrating the data from the low speed storage device to the high speed storage device. Those skilled in the art would understand that, the data block and the data volume here both are logical concepts rather than physical concepts.
In other words, data of a data volume or a data block may be stored on a plurality of physical storage devices. Thus, such a migration is transparent to applications using the data. It can be determined whether or not a data block is a hotspot data block according to a frequency of access to the data block and a response time of access to the data block. If it is a hotspot data block, it is migrated from the low speed storage device to the high speed storage device. However, being frequently accessed in a past period does not mean that the data block will be frequently accessed in a future period.
Therefore, there is a need for a new solution for data migration between storage devices.